If a curl of a certain level or above is generated at an electrolytic copper foil for a lithium secondary battery, a wrinkle may be generated during a battery manufacturing process. If a wrinkle is seriously generated, the electrolytic copper foil may be overlapped. If the electrolytic copper foil is wrinkled or overlapped as described above, a serious defect may occur when manufacturing an electrolytic copper foil for a lithium secondary battery.
Accordingly, when manufacturing an electrolytic copper foil for a lithium secondary battery, it is generally required to control a curl in a level of about 7 mm or below.
Meanwhile, such a curl is generated due to a difference in stress and surface characteristics between both surfaces of a copper foil, namely a shiny surface having relatively higher glossiness and a matte surface having relatively lower glossiness.
For example, due to such a difference in stress and surface characteristics, if a compressive stress is applied to the matte surface, an M-side curl is generated, and if a compressive stress is applied to the shiny surface on the contrary, an S-side curl is generated.
Therefore, in order to control a curl generated at the copper foil to a certain level or below, it is required to find factors giving especially great influences on a curl of the copper foil from surface characteristics of both surfaces of the copper foil, and then control these factors within a certain range.